There are a number of conventional processes for packaging integrated circuits. Many packaging techniques position solder bumps onto associated contact pads formed on an active face of a die to provide electrical interconnects to external devices. The die is then typically attached to a suitable substrate, such as a printed circuit board (“PCB”), such that the solder bumps on the die are surface mounted to solder pads on the substrate. The solder bumps are then reflowed to form solder joint connections between the substrate and the attached die.
Solder bumps and solder joint connections sometimes incorporate polymer/copper balls to maintain the height and structural integrity of the solder joint connections. An example of such a solder bump is presented in FIG. 1. FIG. 1 diagrammatically illustrates solder bump 100 supported by underbump metallization layer (“UBM”) 102 and integrated circuit die 104. Solder bump 100 includes ball 106 and solder material 108. Ball 106 is made of polymer core 112 completely encased in copper shell 110.
Solder bump 100 may be used to connect die 104 with a printed circuit board. Assembly typically involves positioning the solder bump over the contact pad of a PCB. Solder material 108 is then reflowed. Solder material 108, however, tends to collect near UBM 102 and does not readily engage the surface of the PCB. As a result, additional solder material is often added to the PCB. The reflow process connects the solder material on the PCB with the solder material on the die, thus forming an electrically conductive solder joint connection between the two devices.
The above process, however, is not suitable for rework. That is, if the die and/or solder joint connection become defective after assembly, they will have to be replaced. Attachment of another solder-bumped die having similar polymer core balls, however, would again require the application of additional solder material to the PCB. Such pinpoint deposition is sometimes difficult and impractical.
Although existing approaches work well in many situations, there are ongoing efforts to further improve the design of integrated circuit devices, such that problems like those described above are minimized or eliminated.